Comparison of pneumococci isolated from invasive and non-invasive disease in pre-school children

Abstract number: P1712

Aguiar S., Melo-Cristino J., Ramirez M.

Objective: Characterisation of pneumococcal isolates recovered from invasive and non-invasive disease in children with less than 6 years, in Portugal.

Methods:Streptococcus pneumoniae is recognised as an important cause of morbidity and mortality especially among pre-school children. The infections caused by S. pneumoniae range in severity from mild infections such as otitis media to life threatening such as meningitis. Epidemiological studies have shown an association between certain serotypes and invasive infections. Nevertheless, serotype distribution varies considerably in terms of geographic localisation. In this work, we analysed and compared 72 isolates responsible for invasive and non-invasive disease in children with less than 6 years, recovered in 2003. Each isolate, was characterised using a combination of antimicrobial susceptibility profile, serotyping, macrorestriction profiling, using SmaI and pulsed-field gel electrophoresis (PFGE). Multilocus sequence typing (MLST) was performed for representatives of the main PFGE clones obtained.

Results: A significant modification of the distribution of serotypes in 2003 was observed, which included the absence of isolates expressing the main serotype found between 1999 and 2002, namely serotype 14. Nevertheless, molecular analysis did not show a radical change in clonal composition. Serotype distribution among non-invasive isolates differed significantly from the one found in the invasive population. Regarding molecular typing, no marked differences were found among the clonal composition. In terms of antimicrobial resistance, 88.5% and 40.0% of the invasive and non-invasive strains, respectively, were resistant to at least one of the antimicrobials analysed. Among the invasive collection, penicillin and erythromycin resistance decreased in 2003, which was associated with a decline of a small number of serotypes including some present in the heptavalent conjugate vaccine. Regarding non-invasive disease, while penicillin resistance also declined, erythromycin resistance increased considerably in 2003.

Conclusion: The results obtained in the present study indicate that the invasive pneumococcal population is changing in the age groups considered. The absence of serotype 14 isolates and associated clones was the most striking feature of this change, which was not observed among non-invasive isolates. The results indicate that, although related, the two populations are evolving along different lines.

Session Details

Date:

19/04/2008

Time:

00:00-00:00

Session name:

18th European Congress of Clinical Microbiology and Infectious Diseases